Exocytotic release of neurotransmitters from nerve endings was demonstrated ultrastructurally in the taste buds of rat circumvallate papillae by stimulation of high K+ and Ca2+ Ringer perfusion and application of tannic acid-Ringer incubation (TARI) method. Omega-shaped images of large cored vesicles and small clear vesicles, indicating exocytotic release of their contents, were found only in the non-synaptic sites. Occasionally exocytosis occurred at sites facing other nerve fibers. Many coated pits were also seen, which presumably represent membrane retrieval at a later stage of exocytosis. It is likely that the taste buds receive more than one type of innervation.
International Society of Histology and Cytology